Biological aspects of the larva of Sepedophilus testaceus (Coleoptera: Staphylinidae, Tachyporinae): morphology of the posterior abdomen and prey-capture behaviour

Abstract

ABSTRACT Two aspects of the larval biology of the rove beetle Sepedophilus testaceus (Staphylinidae: Tachyporinae) were investigated, namely the morphology of the posterior abdomen (abdominal apex) and the predatory behaviour of the larvae towards elusive springtails. The larvae move their urogomphi via a single urogomphal muscle. Its presumed antagonist is a cuticular, possibly elastic process that lies below the urogomphus. Additional features of the posterior abdomen include (i) a reduced but well-developed musculature, (ii) segmental exocrine glands of unknown function, and (iii) five rectal diverticula that are externally visible as eversible lobes and that presumably serve as adhesive organs. Segments IX and X deviate from the more anterior abdominal segments in both their external and internal organisation including their equipment with muscles. Comparisons with previous studies suggest that the segmental glands and rectal diverticula are groundplan features of Staphylinidae and Staphyliniformia, respectively. However, the structure and biological relevance of these traits have as yet received little attention. Laboratory-based highspeed videography observations have confirmed that the investigated L3 larvae are predaceous and highly capable of capturing even elusive prey such as springtails with a relatively high success rate of 40%. The larvae attack their prey immediately after accidental contact and detect and localise their exact position via the hair-like sensilla on their antennae and other body parts. Contact with the prey is below threshold, i.e. occurs without releasing the prey’s escape response, and is followed by a rapid grasping movement of about 40 milliseconds on average that is executed by the falciform mandibles of the larva. This is well within the range of the escape response of the springtail.